Changes in muscle activity in typically developing children walking with unilaterally induced equinus.

Distinguishing changes in lower limb muscle activation during gait caused by abnormal motor control or adaptations to the presence of a fixed equinus remains a challenge. The objective of this study was to determine a threshold degree of equinus at which changes in muscle activity occur and to characterize adaptive patterns of muscle activity in typically developing children walking with unilateral induced equinus. Ten typically developing children were included. A customized orthosis was fitted to the right ankle. Five conditions of dorsiflexion limitation were evaluated: 10° dorsiflexion, 0°, 10°, 20° of plantar flexion and maximum plantar flexion. Muscle activity of the rectus femoris, vastus lateralis, hamstring, tibialis anterior and soleus muscles of both limbs was recorded. Significant changes in muscle activation and co-activation occurred from 10° of plantar flexion in the orthosis limb and from maximum plantar flexion in the contralateral limb. Soleus activation occurred prematurely in terminal swing and increased with the degree of equinus. Tibialis anterior activation was increased during initial and midswing and was decreased during terminal swing. From the -20° condition, hamstring activation was increased during the loading response. Vastus lateralis and rectus femoris activation was increased during stance phase. Similar changes in tibialis anterior and soleus activation occurred on the contralateral side. Changes in co-activation occurred in the soleus/tibialis anterior muscle pair in both limbs. This study provides indications regarding changes in muscle activity during simulation of equinus gait which should be helpful for therapeutic decision making.

Houx L ，Lempereur M ，Rémy-Néris O ，Gross R ，Brochard S ... -  《-》

Threshold of equinus which alters biomechanical gait parameters in children.

The main aim of this study was to define the threshold angle of equinus beyond which significant changes in 3D lower limb kinematics and kinetics occur in typically developing children and to describe these changes.A customized orthosis was fitted on the right ankle of 10 typically developing children and was adjusted to +10° ankle dorsiflexion, 0°, -10°, -20° plantarflexion and maximum plantarflexion. Gait was analyzed using an optoelectronic system. A gait velocity of 1m/s was imposed.Most of the kinematic and kinetic changes were significantly altered from the -10° condition. In the sagittal plane, the results showed increased knee flexion at initial contact, increased knee flexion or hyperextension in stance, increased hip flexion at initial contact and increased anterior pelvic tilt. Other changes included increased knee varus, reduced hip adduction and more internal foot progression. The ankle plantarflexion moment was bi-phasic during stance, peak ankle power generation was reduced, peak knee extension moment was decreased and hip extension moments increased. On the contralateral side, there was a significant increase in ankle plantarflexion at initial contact and a significant decrease in knee flexion during swing phaseat maximum plantarflexion.Although slight modifications occurred for smaller degrees of equinus, the results suggest that significant kinematic and kinetic changes occurred during gait in both limbs from 10° of plantarflexion. The results of this study also provide some indications regarding the primary causes of gait deviations and secondary compensatory strategiesin children with a clinical dorsiflexion limitation.

Houx L ，Lempereur M ，Rémy-Néris O ，Brochard S ... -  《-》

Does muscle coactivation influence joint excursions during gait in children with and without hemiplegic cerebral palsy? Relationship between muscle coactivation and joint kinematics.

The theoretical role of muscle coactivation is to stiffen joints. The aim of this study was to assess the relationship between muscle coactivation and joint excursions during gait in children with and without hemiplegic cerebral palsy. Twelve children with hemiplegic cerebral palsy and twelve typically developing children underwent gait analysis at three different gait speeds. Sagittal hip, knee, and ankle kinematics were divided into their main components corresponding to joint excursions. A coactivation index was calculated for each excursion from the electromyographic envelopes of the rectus femoris/semitendinosus, vastus medialis/semitendinosus, or tibialis anterior/soleus muscles. Mixed linear analyses of covariance modeled joint excursions as a function of the coactivation index and limb. In typically developing children, increased coactivation was associated with reduced joint excursion for 8 of the 14 linear models (hip flexion, knee loading, knee extension in stance, knee flexion in swing, ankle plantarflexion from initial contact to foot-flat, ankle dorsiflexion in stance and in swing). Conversely, ankle plantarflexion excursion at push-off increased with increasing tibialis anterior/soleus coactivation. In the involved limbs of the children with cerebral palsy, knee loading, ankle plantarflexion at push off, and ankle dorsiflexion in swing decreased, while hip extension increased, with increasing muscle coactivation. The relationships between muscle coactivation and joint excursion were not equally distributed in both groups, and predominant in typically developing children. The results suggest that excessive muscle coactivation is not a cause of stiff-knee gait in children with hemiplegic cerebral palsy, but appears to be related to spastic drop foot.

Gross R ，Leboeuf F ，Hardouin JB ，Perrouin-Verbe B ，Brochard S ，Rémy-Néris O ... -  《-》

Ankle and knee coupling in patients with spastic diplegia: effects of gastrocnemius-soleus lengthening.

Baddar A ，Granata K ，Damiano DL ，Carmines DV ，Blanco JS ，Abel MF ... -  《JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME》

Toe walking in children with cerebral palsy: a possible functional role for the plantar flexors.

Beyaert C ，Pierret J ，Vasa R ，Paysant J ，Caudron S ... -  《-》